# Airworthiness Directives; McDonnell Douglas Model DC-9, DC-9-80 and C-9 (Military) Series Airplanes, and Model MD-88 Airplanes
> **Rule** · Final rule. · Published 1999-10-26 · Effective 1999-11-30 · 64 FR 57551
## Document
- **Document number:** 99-27562
- **Category:** airworthiness
- **Type:** Rule
- **Action:** Final rule.
- **Citation:** 64 FR 57551
- **Publication date:** 1999-10-26
- **Effective date:** 1999-11-30
- **FAA docket:** Docket No. 98-NM-382-AD
## Abstract

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9, DC-9-80 and C-9 (military) series airplanes, and Model MD-88 airplanes, that requires revising the wiring of the air conditioning pneumatic supply control, if applicable, and revising the wiring of the pneumatic augmentation valve. This amendment is prompted by a report indicating that the pneumatic augmentation valve may go fully open when an engine fails during initial climb prior to deactivation of the second segment climb switch. The actions specified by this AD are intended to prevent opening of the pneumatic augmentation valve, which could result in significant loss of thrust from the remaining engine and consequent inadequate initial climb performance of the airplane.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1999/10/26/99-27562/airworthiness-directives-mcdonnell-douglas-model-dc-9-dc-9-80-and-c-9-military-series-airplanes-and)
---
*MORVS · CC0 1.0*